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used and discarded a gas engine, and now has one of Sir William Armstrong's hydraulic engines of ordinary construction. This looks very big and clumsy, and the workmanship is not first-rate. It possesses also the additional disadvantage of running at a very slow speed. Altogether we should have thought a small turbine preferable, and failing that, a steam engine with a boiler heated by gas. Of course when the lathe is being driven by a belt, the treadle crank is unhooked.

The leading screw is driven by a bright set of engine cut change wheels; and from this screw various motions are got for the other movements of the slide rest, which is self-acting on the longitudinal or traversing, the traverse or surfacing, the angular and the curvilinear cuts. These motions, it will be seen, are all contained in a very small space; and the neatness of contrivance indicates the possession of considerable ingenuity on the part of the designer.

The screw headstock has the base slide arrangement for setting out of centre when taper turning, and the usual pinching arrangement at the side for holding the spindle fast, and preventing shake. The cone spindle is shown with the compound eccentric chuck on its nose. It has a large division-plate completely divided; tangent and screw motion for slow rotation; and another arrangement at the side for slow traversing.

The overhead apparatus is very compact and convenient. Its whole arrangement is, however so plainly shown by our illustrations, that a description is scarcely necessary.

1.

MECHANICAL MOVEMENTS.

5. Represents a wheel driven by a pinion of two teeth. The pinion consists in reality of two cams, which gear with two distinct series of teeth on opposite sides of the wheel, the teeth of one series alternating in position with those of the other.

6. A continuous circular movement of the ratchet-wheel, produced by the vibration of the lever carrying two pawls, one of which engages the ratchet-teeth in rising and the other in falling. 7. A modification of No. 10, shown last week, by means of twe worms and worm-wheels.

8. A pin-wheel and slotted pinion, by which three changes of speed can be obtained. There are three circles of pins of equal distance on the face of the pin-wheel, and by shifting the slotted pinion along its shaft, to bring it in contact with one or the other of the circles of pins, a continuous rotary motion of the wheel is made to produce three changes of speed of the pinion, or vice versa.

9. Represents a mode of obtaining motion from rolling contact. The teeth are for making the motion continuous, or it would cease at the point of contact shown in the figure. The forked catch is to guide the teeth into proper contact.

10. By turning the shaft carrying the curved slotted arm, a rectilinear motion of variable velocity is given to the vertical bar,

elder of the two gentlemen entered into conversation with us, the younger undid the package, disclosing a pair of wheels some fourteen or fifteen inches in diameter, to which were attached some stout hickory stirrup-like appendages, in the bottoms of which were foot pieces, shaped like the woods of common skates.

On one side of the stirrup-like appendages were firmly fastened metallic plates, each having a short axle or bearing projecting from its centre, upon which the wheels above-mentioned turned. The stirrup-like appendages were made of flat strips of wood about three inches wide in the broadest portion, bent so that one side was nearly straight, while the other was made to meet it about midway to form a sort of loop. In the bottom of this loop were placed the foot-pieces above described, provided with toe straps and a clasp for the heel. To the upper end of the stirrups was attached a piece of wood to fit the outer and upper conformation of the calves of the legs.

In less time than it took us to note these points the young gentleman-who was subsequently introduced to us as the son of the inventor of this singular device-had strapped on the wheels and commenced rapidly gliding about among chairs and tables with singular swiftness and gracefulness. A space being cleared he proceeded to exe11. A continuous rotary motion of the large cute with seemingly perfect ease, the inside and wheel gives an intermittent rotary motion to the outside roll, figure of eight, &c. &c., amply pinion-shaft. The part of the pinion shown next demonstrating that the "pedespeed" has all the the wheel is cut of the same curve as the plain capabilities of the skate, both in the variety and portion of the circumference of the wheel, and therefore serves as a lock while the wheel makes grace of the evolutions that can be performed a part of a revolution, and until the pin upon the wheel strikes the guide-piece upon the pinion, when the pinion-shaft commences another revolution.

MECHANICAL MOVEMENTS.* (Continued from page 28.) 12. What is called the "Geneva-stop," used A continual rotation of the pinion (ob-in Swiss watches to limit the number of revolutions tained through the irregular-shaped gear at in winding-up; the convex curved part ab of the left, gives a variable vibrating movement to the horizontal arm, and a variable reciprocating movement to the rod, A.

2.

Worm or endless screw and worm wheel. Used when steadiness or great power is required. 3. A regular vibrating movement of the curved slotted arm gives a variable vibration to the straight arm.

4. An illustration of the transmission of rotary motion from one shaft to another, arranged ob liquely to it, by means of rolling contact.

Extracted from a compilation by Mr. H. J. Brown,

Editor of the American Artisan.

the wheel B serving as the stop.

13. Another kind of stop for the same purpose. 14 and 15. Other modifications of the stop, the operations of which will be easily understood by a comparison with 12.

(To be continued.)

THE PEDESPEED. (Illustrated on page 61.)

with it.

of this invention. Of course no mere carpet Our engraving gives an excellent representation knight accustomed to roll about on the common parlour skate, can use these at the first attempt. They require practice; but when skill is once attained, there is skating the year round. Had the "pedespeed

" been introduced on our rinks this winter during the long period stockholders have prayed in vain for ice, their stock would have stood higher in the market than it does at present.

The "pedespeed" is light and strong, and is capable of use on surfaces where the ordinary parlour skate would be useless. The inventor, a large and heavy man, informs us he can use it constantly for two hours without fatigue. For gymnasiums, colleges, and parts of the country where no ice ever occurs, it affords a delightful, healthful, and graceful pastime at all seasons of

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TH

SCIENCE FOR THE YOUNG.

SERIES I.-MECHANICS.

INTRODUCTION.

BY THE REV. E. KERNAN.

THE object of these papers is to lay out for the beginner in Mechanical and Physical science a course from which he will never require to deviate permanently, no matter to what extent circumstances may induce him in after years to increase his scientific acquirements.

Mechanics being the foundation of all true knowledge, claims the first place in a scientific course. The series on mechanics may be divided into three parts. The first sets forth some necessary preliminaries, which, once determined and understood, facilitate the work to come; the second contains all that is usually understood by mechanics in its widest sense; the third treats of bodies in a state of vibration, practically sound, acoustics, which is so closely connected with mechanics that it can be shown to be contained in the definition of this science.

applied to the liquid state has arisen the science | separate chamber, 20ft. by 20ft., and 20ft. high of hydrostatics and hydrodynamics; from their The key notes, or "claviers," as they are techaiextension to the gaseous state has resulted the cally called, are made of massive ivory, and so science of pneumatics. Passing to the confines exquisitely balanced that the least touch is suffiof the ponderable world, to the connecting link cient to sound them, and, in fact, notwithstanding between matter tangible and untangible, sound the size of the organ, any lady could play upon it is discovered to require no new principles. Reach- with the same ease and with the same rapidity as ing farther, to the region of what are usually she could on a cottage piano. If anything, the termed imponderables, the principles of mechanics notes are almost too easily sounded, and scarcely have seized upon light, and made it subject to give that rest for the hand to which organists their unerring laws. By this great conquest are so much accustomed. This, however, is a fault are explained phenomena most complicated and on the right side, and one which will bear good apparently contradictory, which had before been fruits when rapid and brilliant execution is needed For such an elementary course, however, no but an enigma. By it, without fear of error, it to develop the infinite variety of tone of this great great mathematical knowledge is required; the can be shown that in such and such conditions, instrument. All the internal metal pipes are use of simple algebraical formula, some geome- observed which reason would be inclined to re- The front pipes are almost entirely of tin, there certain extraordinary phenomena should be made of an alloy of 5-9ths tin and 4-9ths lead. try, and the first principles of trigonometry are,ject as impossible or absurd; for instance that being 90 parts of that metal to only 10 of lead. as a rule, enough. Where exceptions occur the two lights can be a cause of darkness. It is not The outer pipes are burnished and polished in the means by which full satisfactlon may be obtained surprising, then, to find Dr. Lloyd in his lectures same manner as those of the great continental later on can be indicated. Moreover, in many on light, say of Fresnel, the French philosopher, organs; the burnished metal, in fact, is made the branches of science, the great principles can be ac- who worked out the mechanical theory of light, chief ornament, and a most effective one it is. The quired scientifically, and yet simply, without that that he has "reared the noblest fabric which has organ will be supplied with wind by means of ever adorned the domains of physical science-steam power, as in the case of the Liverpool organ mathematical learning employed for their full Newton's system of the universe alone excepted." in St. George's Hall. Mr. Penn is making two theoretic development by the more advanced Even beyond light has mechanical investigation eight-horse power engines for this work, which scholar. progressed. Heat, less tangible, is being proved, will be able to work up to 50-horse power with every day, more and more, to be but a" mode case and give the very decided pressure of air of motion." The time is perhaps not far off required for playing with full power when all the when electricity shall cease to be that unknown stops are opened. The main reservoirs into which mysterious agent, shall yield its secret to the compressed air is forced are placed in a chammechanics; showing to the wise ones to what a ber in a dry position. The feeders supplying the distance from the truth they have wandered, how air are of a most ample size, and constructed to they have groped in the dark, wasting their receive their wind from the room above, and not energies in theory and speculation. from the locality in which they are placed. To carry out this arrangement, which is one of the highest importance, passages are provided for the windshafts to and from the organ to the chamber in which the main rescrvoirs are placed. The main reservoirs in turn deliver their wind to connection with the pipes. The mechanical numerous subsidiary reservoirs in immediate arrangements effected by the pressure of attenuated and compressed air vary from four to forty inches. The light touch of all the key-notes is alike. The pedal arrangements are divided into ten distinct parts. The external aspect of the. grand organ is very imposing. It is not disfigured by a case. The pipes, carefully graduated as to height, rise in four great clusters of spires, two at each end and two in the centre. In the three sides which front the audience are three vaulted lofty openings which allow all the works to be seen, and in the background is a perfect forest of pipes. The base, or stand, of the organ is about 21ft. high. This is of carved oak with a recessed Italian doorway in the centre, in which, at the keys, the performer sits. The oak screen which forms the external face is, however, merely a screen, for the organ itself is built on massive stone foundations, which the oak work encloses. The instrument will cost, when completed, about £10,000. It has been built under the direct supervision of Sir Michael Costa, assisted by Mr. Bowley, of the Crystal Palace, and Sir Michael pronounced it to be perfect in tone and working.

PART I.-PRELIMINARIES. These may be classed under three heads: The object of mechanics, with the division of the ject; the general properties of matter; and the explanation of terms required for study. CHAPTER I.

OBJECT OF MECHANICS; DIVISION OF THE

SUBJECT.

What, then, is this so much lauded mechanics? It may be differently defined, according to the point from which it is viewed. The following definition will suit the form of the present series: Mechanics is the study of the laws which reguBodies exist in some one of the three states, solid late the action of external forces upon all bodies. sub-liquid or gaseous, and the student cannot begin too soon to keep this triple state of matter before his mind. That solids can be affected by forces requires no proof. For liquids it is only necessary to place a tray with water on a table; the least stir ruffles it's surface; for gases, the rushing of the "thin air," the winds, the storms supply superabundant proof. By the word external is to be understood some manifest action or effort at action; and this effort may be from the nature of the body itself, or from some external source. Thus is mechanical study distinguished from others in which action not directly manifest is the chief object: for instance, chemistry. The study of the laws includes not only the mere statement of them, but also the proofs of their truth, and their actual or possible existence in action, in natural or artificial combinations; in a word, the applications of the principles contained in the laws.

Before answering directly to the question, "What is mechanics?" it would be useful, if not even to a certain extent necessary, to say what it is not. First, then, mechanics is not the method of working in wood or in iron. They who are thus occupied are called "mechanics," but they are not thereby designated as having acquired the science of mechanics. Not but that they could possess it, and would profit much by a knowledge of its principles. Frequently their knowledge is but a mere routine of facts, handed from one to another, the cause of which they do not understand. The small amount of mind required to obtain knowledge of this class, and the fact that such knowledge is not unfrequently combined with great mental deficiency, are the reasons why the "mechanic is not considered as having the higher gifts of intellect. Secondly, the science of mechanics is not the dull, dry study that some imagine.

A

(To be continued.)

A GRAND ORGAN.

THE DETERMINATION OF THE PER-
CENTAGE OF SULPHUR IN IRONS.
THE analysis of irons is becoming increasingly

THE

important, and the small quantities of impurities, which greatly alter their quality, renders accuracy indispensable, and adds to the difficulty of ensuring it. Although not sulphur, but phosphorus, is the greatest hindrance to the production of good iron, being generally present in a larger quantity, the former is nevertheless injurious. It may therefore be acceptable to those who are interested in the subject if I describe the method which has to my mind been the most satisfactory in the estimation of the quantity of sulphur in irons. I have analysed several specimens of pig iron according to the solution in nitrochloric acid method, with all due precautions, which, although exceedingly important, are often omitted in explanations of the process. The following are results of the analyses :

TRIAL has been made of the tone of the grand organ which is being built for the It is quite true mechanics do not possess for Royal Albert Hall, at the works of Mr. Willis, at some the interest which, for example, the bril- Camden-town. This magnificient instrument is liant experimental part of chemistry excites. But remarkable not only on account of its size and the if so it has none of the dull, plodding, mere me- number of its pipes, but also on account of the mory work of theoretic chemistry. Every propo- excellence of its design and construction. It is sition of mechanics sparkles with proof, mathema- 65ft. wide, 70ft. high, and 40ft. deep. It weighs tical and experimental. With a pencil and paper over 150 tons, and has nearly 10,000 pipes in it. the thousand phenomena which may occur are The largest pipes are 2ft. 6in. diameter-the discussed, and their cause, result of combination, smallest about a couple of inches long, and not &c., declared; the instruments are brought for- much thicker than a barley straw. In all there ward, and experiments prove the truth of the are some nine miles length of pipes of various sizes. theory. Again, the constant occurrence within There are no less than 138 stops, 20 couplings, us and around us of the exemplification of me- and 60 combination pedals and pistons. The chanical principles is a new source of interest to extreme range of compass from the highest to the an intelligent mind. So far what mechanics is lowest notes is nine octaves apart. There are four not. Now, on the other side, mechanics is that sets of manual keys and one set of pedals. The part of natural knowledge which best deserves manual keys extend from CC to C in altissimo, the name of a "science." For its principles or sixty-one notes; and the pedal from C C C to have, of all others, been put to the severest of G, or thirty-two notes. The pedal organ consists tests-length of time, found as they are in the of twenty-one stops, the choir organ of twenty very first pages of the history of science; extent stops, the great organ of twenty-five stops, the of application, including, as they do, everything in swell organ of twenty-five stops, the solo organ of the cosmic system that has as yet been brought twenty stops, and there are fourteen couplers. into a really scientific form. And so strictly is Eight pneumatic combination pistons govern the this latter true, that the fundamental principles of whole of the stops of each manual range of keys, mechanics are every day extending themselves to and these are so placed below and in frent of the new branches, rendering clear and logical what was keys as to be at all times within instant reach of the before but a collection of facts, without explana-Lands of the performer. Six pedals govern the tion other than obscurities or contradictions. stops of the pedal organ. The "Swell" is, as Thus from the principles of mechanics of solids usual, in the rear of the organ, and will be in anot make its appearance until after warming the

Sample

1st anal. 2nd anal. Dif.
No. I. per cent, of S. 0:48 0:45 0:03
No. II.
No. III.
No. IV.

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0.62

0.69

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0.07

0:45

0.3

0:15

0.23

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0.26 0.03

The precipitate with chloride of barium does

ORDINARY PUDDLE BARS.

olation for some time. After filtering and chloride of barium was added in large excess,
washing it well with boiling water it is seldom if and the solution heated for some hours and then
ever possible to render it white, which is objec-allowed to stand a whole day and heated again.
tionable to a careful chemist. However, if the It may be interesting to some to give a few of
sulphate is precipitated it all, I am convinced my results :-
that it is entirely precipitated, and with such
results as I have given above there is scarcely
cause to complain much of the process.
As, however, puddle bars contain a very small
quantity of sulphur, at least 10 grammes of iron in
fine powder must be employed in order to obtain
a weighable and reliable quantity of sulphate of
barium. More acid must consequently be used,
and it is impossible to obtain a precipitate in the
strongly acid solution, which, for well known
reasons, must not be neutralised.

I will, therefore, briefly describe the method which I have employed to estimate sulphur in puddle bars and other irons containing small quantities of that element-a method which has given me highly satisfactory results.

And, for circular polarisation :-The Nicols being crossed and the needle pointing to 80° in favour of the platinum spiral, a plate of rock crystal cut perpendicular to the axis was placed across the dark beam. The needle fell to zero, and went to 90% on the other side.

The penetrative power of the heat here 1st anal. 2nd anal. Dif. employed may be inferred from the fact that it I. per cent. of S. 0.038 0:026 0-012 traversed about 12in. of Iceland spar, and about 0.073 0.088 0.015 14in. of the cell containing the solution of iodine. 0 045 0.033 0.015

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Sample.
No.
No. II.
No. III.
One could scarcely expect more satisfactory
results than these are.

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H. B. HAMILTON, Analytical Chemist.

ON THE PHENOMENA OF COM-
BUSTION.

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SPECIAL REPORT.

THE last of the present series of Cantor Lectures on this subject was delivered by ON THE POLARISATION OF HEAT. * Dr. Benjamin Paul, F.C.S., on Monday, 28th BY PROFESSOR TYNDALL, F.R.S., &c. ult., in the presence of a large audience. The In the los te Principal Forbes gave an "N the Philosophical Magazine for November, lecture had specially to do with the use of comA weighed quantity of iron is thrown into a bustible materials for producing light, with the capacious flask (about 2 pints capacity); about account of the experiments by which he demon- varieties of illuminating materials-coal gas, pean ounce of water added, and the whole agitated strated the polarisation of non-luminous heat. troleum, and paraffia oil, and also with the to prevent caking in the after processes. A cork He first operated with tourmalines, and after-measurement of light. At the outset, the lechaving two perforations is inserted into its mouth. wards, by a happy inspiration, devised piles of turer observed that the evolution of light was Into one of these perforations passes a tube with mica plates, which from their greater power of another of the effects of combustion which was of practical utility. It was chiefly by means of combulb and funnel bent and containing a little mer- transmission enabled him more readily and concury to allow of pouring into the flask, but to pre-clusively to establish the fact of polarisation. bustion that artificial light was produced. One vent back action. Into the other passes a tube The subject was subsequently followed up by important fact we had to consider in regard to bent at right-angles leading to a U tube, contain- Melloni and other philosophers. combustion as a source of light was that all maWith great ing caustic potash free from sulphate. (Beyond sagacity Melloni turned to account his own dis- terial substances became luminous when they were sufficiently heated, and this was a special this Utube I placed another containing hydrated covery, that the obscure rays of luminous sources oxide of lead in solution by caustic potash, which were in part transmitted by black glass. Inter- characteristic of solid substances, which, howafter repeated analyses was not in the slightest cepting by a plate of this glass the light emitted ever, were not changed in their condition or degree blackened.) by his oil lamp, and operating upon the trans- nature by such heating. Having shown the Jumitted heat, he obtained effects exceeding in minosity of solid substances by experiment, Dr. magnitude any that could be obtained by means Paul adverted to the fact that liquids also beof the radiation from obscure sources. The came luminous when heated, under conditions, possession of a more perfect ray-filter and a more however, when they were not converted into powerful source of heat enables us now to obtain, vapour. Melted metals and glass, for instance, on a greatly augmented scale, the effects obtained emitted light at high temperatures; gases and by Forbes and Melloni. vapours were least of all capable of luminosity when heated. At a temperature of 1000 degrees, liquid substances emitted a reddish light, and this degree of heat was termed "red heat," which again, in proportion to the temperature, was distinguished by the names "red," or "dall" heat; oragain by those of "cherry red" or "brick red." At very high temperatures, solid and liquid substances gave a colourless light, termed "white heat." To produce artificial light, we must first obtain a very high temperature in some substance capable of becoming luminous in that condition.

SUCTION

Hydrochloric acid is poured in at the funnel, and suction applied to draw it through the mercury into the flask; sometimes water is added, and then acid, until there is a large excesss of acid. When the action, after due addition of acid, is very slow, the contents of the flask are boiled, then the flame taken away, and as soon as ebullition has ceased air is sucked through the apparatus. The boiling can after be advantageously repeated, and the suction again continued. The still caustic solution in the U tube is emptied and rinsed out into a beaker. Pure chlorine gas is passed through it; after boiling, sufficient hydrochloric acid is added to drive off the hypochlorous acid, and the boiling is continued until all or nearly all the smell of this acid is gone. The sulphate is then precipitated with chloride of

Two large Nicol's prisms, such
as those
employed in my experiments on the polarisation
of light by nebulous matter, were placed in
front of an
electrie lamp, and so supported
that either of them could be turned round its
horizontal axis. The beam from the lamp,
rendered slightly convergent by the camera-lens,
was sent through both prisms. But between them
was placed a cell containing iodine dissolved in
bisulphide of carbon in quantity sufficient to
quench the strongest solar light. Behind the
prisms was placed a thermo-electric pile, furnished
with two conical reflectors. The hinder face of
the pile received heat from a platinum spiral
through which passed an electric current regu-
lated by a rheostat.

If hydrogen gas were burned with oxygen, a very intense degree of heat would be attained, but the water vapour which was the product in this gas had such a degree of continuity that it gave a gas affording The apparatus was so arranged that, when the barely sufficient light to be visible. After exprincipal sections of the Nicols were crossed the plaining the production of lime-light, and showneedle of the galvanometer connected with the ing some experiments with magnesia, the lecturer pile showed a deflection of 90° in favour of the adverted to carbon. Carbonaceous substances posterior source of heat. One of the prisms was were easy to illuminate. The chief characthen turned so as to render the principal sections teristic of very inflammable substances was the parallel. The needle immediately descended to presence of carbon, which in some cases was zero, and passed on to 90° at the other side of it. as much as 80 per cent. Oil, tallow, and the Reversing, or continuing the motion, so as to various materials used in lamps were susceptible render the principal sections again perpendicular of vaporisation, and that, too, without giving any asbestos. A small funnel with a rather ill-propor- the needle descended to zero and went up to its case with coal, wood, resin, or such materials. to each other, the calorific sheaf was intercepted, fixed carbonaceous residue, which was not the

barium.

The contents of the flask are filtered through

tioned large neck is chosen. Enough asbestos loosely to fit into the neck is taken and thrown into the funnel, without any placing or pressing with the fingere. On pouring water in to fill the funn el, the pieces of asbestos swim about in the liquid, and gradually settle in the neck in such a manner that the acid solution can be filtered

first position.

heat that a prompt rotation of the Nicol would
So copious, indeed, is the ow of polarised
cause the needle to spin several times round over
its graduated dial.

radiant heat.

These experiments were made with the delicat galvanometer employed in my researches up But the action is so strong as to needles Gin. long and paper indexes a square cause a coarse lecture-room galvanometer, with

Dr. Paul next asked attention to the form of flame, in which the combustible gas was supplied, and which, he said, was partly determined by the way partly by the reaction of the heated product of combustion and the atmosphere upon each other. The shape of the luminous flame might be different from that of a candle, but in every case there was the same relative disposition of the place. The production of flame from any subzones in which the progressive changes took

quickly and perfectly clearly. After it has all gone through, the flask need not be rinsed out, or the residue in funnel washed; but the latter should be transferred with the asbestos to the inch each in area, to move through an arc of stance corresponded to the amount of carbon it

flask again, and the funnel washed with a very small quantity of nitrochloric acid, which is allowed to trickle into the flask also. The black residue mixed with nitrohydrochloric acid in very small quantity is heated, covering the mouth of the flask with a glass plate. Some water and

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carbonate of soda is added to take off the excess
of acid, and the liquid, after boiling, is filtered
Take, for example, the following experiments:
through paper, taking care that it is still slightly-The Nicols being crossed, the needle of the
acid, and, of course, washed. Chloride of barium galvanometer pointed to 788 in favour of the
is added to this solution, and if, as is often the heated platinum spiral behind the pile. A plate
case, a precipitate be produced, the whole is of mica was then placed across the dark beam
poured into the beaker with the former precipi- with its principal section inclined at an angle of
tate, and treated in the usual manner. By this 45 to those of the Nicols. The needle instantly
method I obtained highly satisfactory results from fell to zero, and went up to 90% on the other side.
irons which, according to the other process, would
not show the least sign of precipitation when
From the Philosophical Magazine.

contained, and to this was owing the difference coal gas. After some remarks on the comparative between the flame from a candle and that from merits of olefiant, marsh, and benzole gases, the lecturer alluded to paraffin oil, and said that, whereas marsh gas contained 75 per cent of carbon, paraffin oil contained 85, and the former contained half as much carbon as olefiant gas. The vapour of marsh gas contained one-seventeenth much carbon in a given volume as the vapour of paraffin, which was very much more dense. The same was the case with benzole gas, which contained four times as much carbon as an equal volume of marsh gas. The latter gas burnt with a pale flame, leaving no sooty deposit or luminous effect, and the former burnt with an intensely luminous flame, and over and above

as

that left a large deposit of carbon, which, unless regulated, rendered the flame sooty and smoky. In all illuminating materials it was necessary to regulate the conditions in such a way that we might get a deposit of carbon to such an extent as would make a flame in the highest degree luminous, without overstepping the line at which it became smoky. The lecturer next referred to the heat of rooms, and observed that most people seemed to forget that in proportion to the quantity of artificial heat introduced into a room in that proportion was the air deteriorated. Olefiant gas produced the greatest effect upon the atmosphere, by destroying the largest amount of air; marsh gas next; carbonic acid gas next, and hydrogen gas least of all, because it was the most volatile. Dr. Paul then referred to the complaints so rife relative to the bad quality of the gas now supplied, and said that although these complaints might to some extent be based on just grounds, yet he thought much of the fault lay with the burners in use. He here exhibited some of Mr. Sugg's improved burners, and con

cluded by regretting that the time at his disposal had prevented him from entering into the interesting subject of paraffin oil.

We understand that the next series of Cantor Lectures will be given by Dr. Williams, on "Fermentation," and that they will take place on the last two Mondays in April, and the first two Mondays in May.

STRUCTURE OF THE LIVER.

AN important paper on this subject by Professor Hering, of Vienna, appears in the just published third part of Stricker's Handbuch von den Geweben. This gland is the most intricate in the body of the higher animals, and its functions present a corresponding complexity; on these grounds it has been subjected to very careful microscopical examination, as well as experimental investigation, by many of the best observers, both here and abroad, amongst whom Professor Hering holds a distinguished place. Speaking broadly, the liver consists of an immense number of pear-shaped bodies or lobuli, separated from one another by a delicate investment of connective tissue. Between these spread branches of the portal vein, conveying blood to the liver from the intestines, and of the hepatic artery, the ultimate branches of the latter discharging themselves into those of the former. The capillary vessels thus formed penetrate the substance of each lobule and reunite in a central vessel, which, issuing from the extremity of the lobule like the stalk of a pear, coalesces with others to form the hepatic veins which convey the blood that has circulated through the organ to the heart. The substance of the lobuli themselves is composed of cells, the office of which is in part to secrete bile, and in part to produce the substance termed glycogen. The writer observes that the capillary system of the portal vein, as a general rule, exhibits large capillaries and a narrow-meshed plexus, whilst that of the hepatic vein exhibits small capillaries and a plexus with wide meshes. The foregoing facts are now fairly established, but the points to which Professor Hering's attention has been particularly directed are connected with the distribution of the biliary ducts. These, he states, consist of a close net work of delicate canals running between the hepatic cells, with meshes equalling the cells in diameter, or, in other words, the canals run between the flat surfaces of two adjoining cells. The capillaries, on the other hand, occupy the angles formed by the junction of three or more cells. This description particularly applies to the rabbit. In man and the dog, biliary canals are also found at the angles of the cells. For the sake of clearness, we have made use of the term biliary canals, but Professor Hering observes that they have no proper wall so long as they are contained within the lobuli. These walls are, in fact, the cells themselves, and they may fairly be represented by the tubes that would be produced by grooving two solid bodies, another. He has not been able, in any instance, and applying the corresponding channels to one in the rabbit at least, to discover a blind extremity of a biliary tube. He describes the hepatic cells as presenting various forms, according to the direction in which they happen to be divided in the section, being sometimes quadrangular, sometimes polygonal, and presenting the grooves above mentioned for the passage of the capillaries, and for the formation of the ducts. They contain one,

or occasionally two, nuclei of spherical or elliptic shape, together with some granules of biliary pigment and fat molecules. He finds the liver to be richly supplied with lymphatics, which, as in other organs, chiefly accompany the connective tissue. The system presents this peculiarity, however, that both the capillaries and the larger vessels freely anastomose with each other. Though he has carefully examinedt he point, he has been unable to follow the nerves of the liver into the cells, a relation which has been maintained to exist by Pflüger. (Academy, No. II., p. 47.) Professor Hering states distinctly that all demonstrable nerve trunks lie outside the lobuli.

PLATINISED LOOKING-GLASSES.*

BY C. WIDEMANN.

NO. III

(Continued from page 27.)

T is now unnecessary to use glass free from colour or to require parallelisms of the time surfaces. Bubbles of air, stripes, foreign bodies, pieces of the pots, &c., &c., do not interfere with the process. There is then an economy of 50 per cent. in the glass.

In order to manufacture a looking-glass of 5 millimetres thickness, they use at the St. Gobain works a plate measuring 10 millimetres thickness. At the Wailly-sur-Aisne works, plates are used having but 7.5 millimetres thickness, as it is only necessary to polish the glass on one side. From

this a saving is made of 25 per cent on the thickness of the glass.

Very correct calculations show that Mr. Dodé secures an economy of 50 per cent. on platinised glasses, as he uses for that purpose only inferior glass commonly used for flagons; even common brittle glass can be used without the least difficulty. To this saving there is another te be added, which will astonish the reader. A square metre of glass absorbs abont 183 grammes of mercury and 550 grammes of tin, representing about a cost of 4 francs, 40 centimes. A yard of platinised glass costs 1 franc and 20 centimes for platina. It results from this, that at the Wailly-sur-Aisne works, the superficial square yard of platinised glass is sold at an average of 25 francs. This price is doubled in the mercury manufacture.

square

There is another circumstance for which this new process is recommended to the public. It is with great difficulty that mirrors are obtained with a curved surface. By the platina process this difficulty disappears, and it is as easy to manufacture curved, round, etc., as horizontal mirrors. There is also no inconvenience arising from upsetting the glasses in transportation or in placing them in the frame.

a spectre; this photograph is simply applied at the posterior side of the reflecting part, and oiled in order to add to its transparency. This toy is varied in very different ways, and has just been applied in the new play of "The White Cat," at Paris, and has caused an immense sensation. So I have no doubt that the inventive mind of the Americans will find thousands of applications for this property, either in applying it to the decoration of stores, or to external ornamenta tion. In theatres or concert halls among flowers it produces the most fairy-like effect. The window glasses of a parlour made thus would transparent in daytime, and at night when the shutters are closed the whole window woud appear as a large looking-glass, and reflect all lights and objects in the apartment.

The manufacture of glasses with amalgam necessitates great labour. In order to obtain 50 metres of looking-glass a large number of hands and a large plot of ground are required. These glasses must remain loaded with weights from 15 to 20 days; then 20 days more are required to three months more are required before they are eliminate the superabundance of mercury, and saleable; not to mention all the precautions that have to be taken at every moment in the shipping and setting in frame. MM. Dode and Faure are able to platinise a surface of 800 metres a day, with only the aid of a few hands, as one workman is able to platinise 50 metres of glass

in 12 hours' work.

EXHAUST STEAM FOR HEATING PURPOSES.

BY CHARLES E. EMERY. UESTIONS are frequently asked regarding

the relative economy of heating buildings with live steam taken direct from the boiler, or with the exhaust steam from a non-condensing engine.

Though the steam engine is a heat engine, the best examples utilise only ten per cent. of the heat in the steam used, consequently at least 90 per cent. of the heat which enters the cylinder escapes with the exhausting steam, and can be made available in no way except for heating

purposes.

The temperature of the exhaust steam from a condensing engine is from 130 to 1408 Fahr., and that from a non-condensing engine is from 2129 to 2208 and upward, varying aecording to the amount of back pressure in either ease. A portion of the escaping heat is generally utilised in heating the feed-water for the boiler. In the condensing engine the low temperature of the exhaust steam, and the liability to air leakages and Already in this country a company has been loss of vacuum in long pipes, makes it impracticable organised to manufacture reflectors by the means to save any more of the heat than that mentioned, of silver mica leaves on the posterior face, and and the remainder is necessarily wasted in heating fastened together so as to obtain a large reflective the condensing water. In the non-condensing surface possessing the desired curves. They are engine there is on the average ten per cent. of the cheap, and easily repaired; but they meet with heat utilised by the use of a feed-water heater, in two great difficulties: the quick alteration of the addition to the ten per cent. transmuted into work, silvery surface caused by the hydrosulphurous consequently eighty per cent. of the original gases of coal with which locomotive reflectors amount of heat remains in the exhaust steam, and are always in contact, and the want of trans- is usually wasted in the atmosphere. If this large parency of the mica and its yellow colour. I quantity could be used for heating buildings withhave no doubt that by the adoption of the pla-out interfering with the performance of the entina these evils would have found their remedy, for, as it has been seen before, the reflecting surface is on the anterior part of the glass.

gine, there would be no doubt of the value of the system-the heat in fact would cost nothing; but it is evident that in order to cause this steam

to traverse through heating-pipes and coils it must have sufficient pressure in excess of that of the atmosphere to enable it to overcome the increased resistance. The additional pressure varies from two to five pounds and upwards per square inch, and acts as so much back pressure upon the piston, thereby reducing the power of the engine. The power lost must be supplied by increasing the mean pressure upon the driving side of the relative cost in fuel of supplying the heatingpiston, and the question becomes :-What is the is pipes with steam direct from the boiler, as comthe building? pared with that required for the extra power necessary to circulate the exhaust steam through

A quite peculiar property of the platinised mirrors will no doubt be applied by architects. The platinised glasses forming mirrors are transparent when the light passes through them. A person placed in the rear of an office can see everything going on in the front office without himself being seen. I insist particularly on this property; appears to me to give to the platinised glass quite a new application, which will increase its sale. This transparency is easily explained considering the small quantity of platina deposited on the glass, which quantity prevent the luminous rays from passing through not large enough to give opacity to the glass and it. This transparency has received a very amusing application quite lately in Paris. Mirrors called mirrors a surprise, are sold, which, when a black paper at the back of the glass is removed, allows a photograph or any other image to be seen through the metallised surface appearing as

* From the Scientific American.

The answer to this problem depends upon the particular circumstances of each case, and to make the subject generally understood, it is first necessary to investigate some of the known facts in regard to low-pressure steam-heating appara

tus.

Manufactories where steam-power is employed

in square inches, and the speed of piston in feet
per minute, and divide the product by 33,000.*

generally have a large number of windows for
the convenience of the workmen, and are often
more or less exposed to cold draughts from hoist- The next step is to ascertain the coal required
ways, staircases, and outer doors, and though the per horse-power per hour. This should be done,
temperature need not be so high as in dwelling- when practicable, by regular experiment. In
houses, it would be unsafe to allow less than one other cases, it may be assumed that engines
square foot of heating surface in the heating pipes working with a steam pressure of 50lb. and
and coils to every 100 cubic feet of space to under, with little expansion, will require 5 to
be heated. In order to form a safe estimate of 61b. of coal per horse-power per hour. With
the amount of fuel required when the steam is more expansion, 4 to 5lb. will be required; and
taken direct from the boiler, we may assume as the most improved form of expansive engines,
an extreme case that the difference between the working with steam at 80lb. pressure, will
external air and that of the room is to be 69; furnish a horse-power for 3lb. of coal per hour.
then, according to the experiments and formula By multiplying the horse-power due to the in-
of Tredgold, we find that it will require three creased back pressure by the coal required per
and one-eighth square feet of surface to eon-horse-power per hour, and the product by 2500,
dense a pound of steam per hour, and if one the result will be the least number of cubic feet
pound of coal evaporate eight pounds of water, of space which can be heated economically by the
it will supply steam to (8 x 3.125) 25 square exhaust steam from that engine. The advantages
feet of heating surface and will heat (25 x 100=) under different circumstances may be ascertained
2500 cubic feet of space for one hour. This in the manner previously stated.
estimate will be correct for average circumstances,
but will not apply to all cases of low-pressure
steam-heating, especially where the rooms are
unusually exposed either to draughts of air, or
great extremes of temperature.

In estimating the greatest amount of space that can be heated by the exhaust steam of an engine, it should be borne in mind that the quantity of steam discharged necessarily varies with the work being done, and as the temperature of the building requires to be constant, we can only utilise the quantity of heat escapiog when the engine is lightly loaded. For instance, an engine of 80-horse power may be loaded occasionally to only 40-horse power for half an hour or more at a time. If each horse power require on the average 3lb. of coal per hour, 40-horse power will require 1201b. As has been before mentioned, the exhaust steam from an engine contains 8-10ths of the heat received from the fuel, so in the present case the maximum heating effect is equal to 8-10th of 120lb., or 961b. of coal per hour; and as each pound of coal will beat 2500 cubic feet of space, 95lb. will heat 240,000 cubic feet, equal to the capacity of a building 100ft. long, 60ft. wide, and 40ft. high. The extra power required to overcome the back pressure in that sized engine could not well exceed 10-horse power, which would cost 30lb. of coal per hour; direct from twould be required were steam taken from the boiler, the saving is (96-30) 661b. per hour, or 68 per cent. If the quantity of space heated be less than that mentioned, the percentage of saving will be less; for instance, to heat 150,000ft. of space in the ordinary way would require 601b. of coal per hour; but with the exhaust steam in the above instance the cost will still be 30lb., so the saving will be 50 per cent. In warm days in winter, when less heat is required in the buildings, the same power will be taken from the engine to supply the less quantity of heat, so that the percentage of saving will be less. There would be some saving, however, whenever it required more than 301b. of coal to heat the rooms. In case each horse power required more coal per hour than that stated, the advantages of exhaust heating would be correspondingly diminished, unless the size of the engine and amount of power pecessary to distribute the steam were also less. In some instances, probably, the system is productive of loss as compared with the use of live steam, so the true plan is to make accurate calculations in each case. The following directions may therefore assist many readers

In heating a building by exhaust steam, particular attention should be given to the size and arrangement of the pipes. A main exhaust pipe should be run up through the building and out of the roof in the usual manner. This pipe should be larger than is ordinarily employed, so as to form a kind of expansion chamber to equalise the exhaust pressure. From the vertical exhaust pipe the heating pipes may be led out for each floor of the building. A common plan is to put a good-sized cast-iron pipe under the workbenohes along the sides of the rooms. Such pipes should be connected by bolted flanges, and ample provision made for expansion and contraction. Heating coils of the ordinary construction may also be used, care being taken to make the leading pipes with as few bends as possible and of sufficient size. To obtain the proper size of pipe for a given case, the following formula may be used, which is founded on some experiments made by the writer for the United States Government, viz.: a W46 (p + 3) in which a area of steam-pipe in square inches, W the weight of steam in pounds delivered per hour, and p the difference in pressure. Assuming as an extreme that 2:4 square feet of surface (s) will condense one pound of exhaust steam per hour, then, when the difference in pressure equals one pound, a = s

=

REVIEWS.

Continental Farming and Peasantry. By JAS.
HOWARD, M.P. London: W. Ridgway, 169,
Piccadilly.

THE comparison of results obtained from two opposite systems must always decide the question. Mr. Howard's book in this manner contributes to settle the question of large or small farming. Travelling himself through the farming districts of France and Belgium, where small holdings prevail, he shows not only that the produce does not equal that of English farming, but that the holders are worse off; do more work for less money with less results than English farm labourers, although possessed of the advantages of a more favourable climate. Mr. Howard would permit small holdings on large estates as rewards held out by the owner (as in the case of Lord Lichfield) to deserving and thrifty workmen in later life. He would not, however, encourage the sub-division of holdings into smaller lots. One fact which he calls attention to is worth notice, namely, that in Belgium, where the small farm system is said to obtain such favour, the Trades' Union Congress, which met some time back at Brussels, condemned the system of "petite culture," and resolved that when communism in land was gained it would be necessary to farm on a large scale in order to take advantage of machinery, &c., in the production of food.

Every Man His Own Lawyer. By A BARRISTER. London Lockwood and Co., Stationers'-hallcourt, E.C.

THE eighth edition of this useful book needs little more from us than mention. For 68. 8d. our readers can obtain a trusty adviser in every point of law, whose first charge is his only one, and who will not advise with a view to litigation and long bills, as lawyers in the flesh too often do.

MATHEMATICS,

BY C. H. W. BIGGS, (Continued from page 628, Vol. X.) RECAPITULATORY EXERCISES IN FRACTIONS.

440. The following is then a safe rule :Divide the heating surface in square feet by 400, § 32.The following exercise hirules already given.'s the result is the proper area of the pipe in square inches. The following table gives the amount of surface which will be supplied with steam through pipes of the sizes mentioned:

Diameter of Pipe.
inch

Amount of Surface.
40 square feet

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the condensed water will move in the same direc-
The pipes should be slightly inclined, so that
tion as the steam. The ends of the various heat-
ing pipes and coils should be connected with a
water-pipe terminating near the boiler in an in-
verted siphon, the shorter leg of which should be
under ground if necessary. This siphon should
about seven feet long. The bend may extend
deliver the condensed water into a tank where it
can be returned to the boiler. An air-cock should

be placed in the water-pipe to allow the air to
escape in starting.

To ascertain whether heating by exhaust steam haust steam can be shut off from each room ɛepaArrangements should be made so that the exis economical where it has already been applied, rately by a valve, and in some instances it may be the first step is to measure the extra back pres-desirable to admit live steam into portions of the sure on the piston, which can be done by indi

cating the engine when the steam is escaping pipes when the engine is not in motion. Amerifreely into the atmosphere, and when the can Artisan.

exhaust is throttled for

heating purposes,

and comparing the back pressures shown by

THE LUMINOSITY OF PHOSPHORUS.-Herr

the diagrams. If this be not convenient, W. Muller, of Perleberg, gives an explanation of the
one leg of an inverted glass siphon containing well-known luminosity exhibited by phosphorus in
mercury may be connected to some enlarge-nation with oxygen, but does not take place in pure
the dark. It depends on slow combustion or combi-
ment of the exhaust-pipe, and the mean difference oxygen, except when it is diluted by other gases, as is
in level noted in the two cases the same as before. the case in the atmosphere. In other atmospheres, as
One pressure corresponds to about 2 (2037) hydrogen or nitrogen, the phenomenon does not occur.
inches of mercury. A longer syphon filled with
water may be used with some inconveniences.
In such case, one pound pressure corresponds to
a column of water 2-3 feet high and 60° tempera-
ture, or 2-4 feet high at temperature of 205°.

Having ascertained the extra back pressure, the horse-power required to overcome it may be ascertained by the following rule, viz.: Multiply together the back pressure, the area of the piston

Many engineers will find the following formula
more convenient :-
d's r p
252,000

H.P. =

which, put in the form of a rule, is: Horse-power
equals the square of the diameter (d) in inches, multi-
plied by the length of a single stroke (3) in inches,
multiplied by the number of revolutions per minute
divided by 252,000.
(r), multiplied by the extra back pressure (p), and

capacities applying

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